AN INVARIANT IMBEDDING ANALYSIS OF GENERAL WAVE SCATTERING PROBLEMS

The invariant imbedding technique, via the solution of a Riccati-type equation, is modified to calculate the wave fields inside and scattere d from a strongly (laterally and vertically) heterogenous, anisotropic inclusion, which may be large but remains compact. The factorization underlying this approach is carried out with respect to direction of a verage power how rather than the more conventional factorization with respect to local direction of propagation. The solution of the operato r Riccati equation is related to the Dirichlet-to-Neumann map. The for mulation is robust in the sense that it can handle a rather extreme ra nge of modal wave speeds, acid allows continuous as well as discontinu ous medium variations on different (wave) length scales. It also, inhe rently, takes care of critical-angle phenomena. The algorithm, based o n the invariant imbedding approach, yields the internal fields for a f ull survey of sources and receivers simultaneously. The wave field sol ution in the inclusion is coupled to the external field via a boundary element approach. (C) 1996 American Institute of Physics.